Oxidative dehydrogenation process



United States Patent Ofiice 3,308,196 Patented Mar. 7, 1967 3 308 196 oXInATivE nErrYbRdoENArIoN PROCESS Laimonis Bajars, Princeton, N.J., assignor to Petro-Tex Chemical Corporation, Houston, Tex., a corporation of Delaware No Drawing. Filed Oct. 22, 1965, Ser. No. 502,581 16 Claims. (Cl. 260-680) This application is a continuation-in-part of my earlier filed pending application Serial Number 250,019 filed January 8, 1963, entitled, Process of Dehydrogenation, now abandoned, which in turn was a continuation-in-part of my now abandoned applications Serial Number 52,776 filed August 30, 1960, entitled Improved Dehydrogenation Process, Serial Number 145,992 filed October 18, 1961, entitled, Dehydrogenation of Hydrocarbons, Serial Number 145,993 filed October 18, 1961, entitled, Dehydrogenation Process, Serial Number 156,955 filed December 4, 1961, entitled, Process of Dehydrogenation, Serial Number 156,957 filed December 4, 1961, entitled, Dehydrogenation Method, and Serial Number 207,105 filed July 2, 1962, entitled, Improved Dehydrogenation Process.

This invention relates to a process for dehydrogenating organic compounds and relates more particularly to the dehydrogenation of organic compounds in the vapor phase at elevated temperatures in the presence of oxygen, bromine and an improved inorganic contact mass.

- It has been found recently that a great variety of dehydrogenatable organic compounds may be dehydrogenated by reacting a mixture of an organic compound containing at least one pair of adjacent carbon atoms, each of which possess at least one hydrogen atom, bromine or a bromine-liberating material, and oxygen under specified conditions at an elevated temperature, and at a reduced partial pressure of the organic compound, in the presence of certain metals or compounds thereof to obtain the corresponding unsaturated organic compound containing at least one pound of Periodic Table 1 Groups IVb, Vb, and VIb.

The process of this invention can be applied to a great variety of organic compounds to obtain the corresponding unsaturated derivative thereof. Such compounds normally will contain from 2 to 20 carbon atoms, at least one t C C l grouping, that is, adjacent carbon atoms each containing at least one hydrogen atom and having a boiling point be- Periodic Table, e.g., is found in Smiths Introductory College Chemistry, 3rd edition (Appleton-Century-Crofts, Inc., 1950).

low about 350 C. Such compounds may contain in addition to carbon and hydrogen, oxygen, halogens, nitrogen and sulphur. Among the classes of organic compounds which are dehydrogenated by means of the novel process of this invention are alkanes, alkenes, alkyl halides, ethers, esters, aldehydes, ketones, organic acids, alkyl aromatic compounds, alkyl heterocyclic compounds, cyanoalkanes, cyclo-alkanes and the like. Illustrative dehydrogenation include ethylbenzene to styrene, isopropylbenzene to a-methyl styrene, ethylcyclohexane to styrene, cyclohexane to benzene, ethane to ethylene and acetylene, ethylene to acetylene, propane to propylene, isobutane to isobutylene, n-butane to butene and butadiene-1,3, butene- 1 to butadiene-l,3 and vinyl acetylene, cis or trans butene- 2 to butadiene-l,3, butane or butene to vinyl acetylene, butadiene-1,3 to vinyl acetylene, methyl butene to isoprene, isobutane to isobutylene, propionaldehyde to acrolein, ethyl chloride to vinyl chloride, propionitrile to acrylonitrile, methyl isobutyrate to methyl methacrylate, and the like. Other representative materials which are readily dehydrogenated in the novel process of this invention include ethyl toluene, the alkyl chlorobenzenes, ethyl naphthalene, isobutyronitrile, propyl chloride, isobutyl chloride, ethyl fluoride, ethyl dichloride, butyl chloride, the chlorofluoroethanes, methylethyl ketone, diethyl ketone, methyl propionate, and the like. This invention is useful in the preparation of vinylidene compounds containing at least one CH C group, that is, a compound possessing at least one group containing a terminal methylene group attached by a double bond to a carbon atom, and 2 to 12 carbon atoms and is particularly useful in the dehydrogenation of hydrocarbons containing 2 to 5 carbon atoms or aliphatic nitriles of 3 to 4 carbon atoms. Preferred compounds to be dehydrogenated are hydrocarbons of 4 to 8 carbon atoms having at least four contiguous non-quaternary carbon atoms. Aliphatic acyclic hydrocarbons of from 4 to 5 or 6 carbon atoms are preferred. The invention is further particularly adapted to provide butadiene-1,3 from butane and butene and isoprene from isopentane and isopentene in high yields and excellent conversion and selectivity.

As shown by the examples below and the disclosures herein, the novel process of this invention is applicable to a great variety of organic compounds containing 2 to 20 carbon atoms and at least one pair of adjacent carbon atoms bonded together and each carbon atom possessing at least one hydrogen atom including the following: hydrocarbons including both alkanes and alkenes, especially those containing 2 to 6 0r 8 carbons; carbocyclic compounds containing 6 to 12 carbon atoms, including both alicyclic compounds and aromatic compounds of the formula wherein Ar is phenyl or naphthyl, R is hydrogen or methyl and X and Y are hydrogen or alkyl radicals containing 1 to 4 carbon atoms, or halogen; alkyl ketones containing 4 to 6 carbon atoms; aliphatic aldehydes containing 3 to 6 carbon atoms; cyanoalkanes containing 2 to 6 carbon atoms; h-alo-alkanes and halo-alkenes containing 2 to 6 carbon atoms, particularly chloroand fluoro-alkanes and the like. Vinylidene compounds containing the CH C group, that is, containing a terminal methylene group attached by a double bond to a carbon atom, are readily obtained from organic compounds containing 2 to 12 carbon atoms and at least one group wherein adjacent carbon atoms are singly bonded and possess at least one hydrogen each. For example, vinylidene halides; vinyl esters; acrylic acid and alkyland halo-acrylic acids and esters; vinly aromatic compounds; vinyl ketones; vinyl heterocyclic compounds; diolefins containing 4 to 6 carbon atoms, olefins containing 2 to 8 carbon atoms, and the like are obtained as products. The vinylidene compounds normally contain from 2 to 12 carbon atoms and are well known as a commercially useful class of materials for making valuable polymers and copolymers therefrom.

Useful feeds as starting materials may be mixed hydrocarbon streams such as refinery streams. For example, the feed material may be the olefin-containing hydrocarbon mixture obtained as the product from the dehydrogenation of hydrocarbons. Another source of feed for the present process is from refinery by-products. Although various mixtures of hydrocarbons are useful, the preferred hydrocarbon feed contains at least 50 weight percent butene-1, butene-2, n-butane and/ or butadiene- 1,3 and mixtures thereof, and more preferably contains at least 70 percent n-butane, butene-1, butene-2 and/or butadiene-l,3 and mixtures thereof. Any remainder usually will be aliphatic hydrocarbons. The process of this invention is particularly effective in dehydrogenating acyclic aliphatic hydrocarbons to provide a hydrocarbon product wherein the major unsaturated product has the same number of carbon atoms as the feed hydrocarbon.

Bromine may be employed as free bromine or as any bromine-containing material which liberates the specified amount of free bromine under the conditions of reaction as defined hereinafter. For example, bromine, hydrogen bromide, the alkyl bromides, such as methyl bromide and ethyl bromide, wherein the alkyl groups preferably contain 1 to 6 carbon atoms; ammonium bromide and the like. Additional bromine compounds are bromohydrins such as ethylene bromohydrin; bromo substituted aliphatic acids such as bromacetic acid; organic amine bromide salts such as methyl amine hydrobromide; and other bromide compounds such as, SBr CHBr CBr and the like. Generally, the bromine compound will have a boiling or decomposition point of less than 400 C. and usually no greater than 100 C. Preferred are ammonium bromide, molecular or elemental bromine and/or hydrogen bromide. It is an advantage of this invention that hydrogen bromide or ammonium bromide may be employed as the bro-mine source, with one advantage being that the hydrogen bromide or ammonium bromide in the effluent from the reactor may be fed directly back to contact the hydrocarbons in the dehydrogenation reactor Without any necessity of converting the hydrogen bromide to bromine. It is understood that when a quantity of bromine is referred to herein, both in the specification and the claims, that this refers to the calculated quantity of bromine in all forms present in the vapor space under the conditions of reaction regardless of the initial source or the form in which the bromine is present. For example, a reference to 0.05 mol of bromine would refer to the quantity of bromine present whether the bromine was fed as 0.05 mol of Br or 0.10 mol of HBr.

The amount of bromine usually will be in an amount greater than about 0.0001 mol of bromine, such as at least 0.001 mol, or the equivalent amount of bromineliberating material per mol of organic compound to be dehydrogenated, more usually at least about 0.01 mol equivalent of bromine per mol of organic compound will be employed. Large amounts of bromine may be used, as high as one-half to one mol or more per mol of organic compound to be dehydrogenated, but it is one of the unexpected advantages of this invention that only very small amounts of halogen are required, normally less than about 0.2 mol total equivalent of bromine and more desirably less than 0.1 mol of bromine per mol of organic compound to be dehydrogenated. Amounts of bromine between 0.001 or 0.005 and 0.08 or 0.09 mol of bromine per mol of the organic compound to be dehydrogenated are preferred, with the range of about 0.01 to 0.05 being particularly preferred. Preferably the bromine will be present in an amount no greater than 5 or 10 mol percent of the total feed to the dehydrogenation Zone.

The amount of oxygen employed will normally be at least about one-fourth mol of oxygen per mol of organic compound to be dehydrogenated. Generally greater than 0.25 mol of oxygen per mol of the organic compound will be used. Excellent yields of the desired unsaturated derivatives have been obtained with amounts of oxygen from about 0.4 to about 1.5 mols of oxygen per mol of organic compound, and within the range of about 0.25 or 0.4 to 2 mols of oxygen per mol of organic compound economic, production and process considerations will dietate more exactly the normal ratio of oxygen to be used. A preferred range for oxygen is from 0.5 to 1.2 mols of oxygen per mol of compound to be dehydrogenated. Large amounts of oxygen may be used with short contact time and high dilutions as with steam, for example, 30 to 50 mols per mol of organic compound. Oxygen is supplied to the reaction system as pure oxygen, or as oxygen diluted with inert gases such as helium, carbon dioxide or as air and the like. In relation to bromine, excellent results are obtained when the amount of oxygen employed is greater than one mol, as 1.25, of oxygen per atom of bromine present in the reaction mixture, usually greater than about 1.5 mols of oxygen per atom of bromine. Usually the ratio of the mols of oxygen to the mols of bromine will be at least 3 such as from 5 or 8 to 500 and preferably will be between 15 and 300 mols of oxygen per mol of bromine.

While the total pressure on systems employing the process of this invention normally will be at or in excess of atmospheric pressure, vacuum may be used. Higher pressures, such as about or 5200 p.s.i.g. may be used. The partial pressure of the organic compound under reaction conditions usually will be equivalent to 'below 10 inches mercury absolute when the total pressure is atmospheric. Better results and higher yields of desired product are normally obtained when the partial pressure of the organic compound is equivalent to less than about one-third or one-fifth of the total pressure. Also because the initial partial pressure of the hydrocarbon to be dehydogenated is generally equivalent to less than about 10 inches of mercury at a total pressure of one atmosphere, the combined partial pressure of the hydrocarbon to be dehydrogenated plus the dehydrogenated hydrocarbon will also be equivalent to less than about 10 inches of mercury. For example, under these conditions, if butene is being dehydrogenated to butadiene, at no time will the combined partial pressure of the butene and butadiene be greater than equivalent to about 10 inches of mercury at a total pressure of one atmosphere. Preferably the hy' drocarbon to be dehydrogenated should be maintained at a partial pressure equivalent to less than one-third the total pressure, such as no greater than six inches or no greater than four inches of mercury, at a total pressure of one atmosphere. The desired pressure is obtained and maintained by techniques including vacuum operations, or by using helium, organic compounds, nitrogen, steam and the like, or 'by a combination of these methods. Steam is particularly advantageous and it is surprising that the desired reaction to produce high yields of product are effected in the presence of large amounts of steam. Steam is particularly advantageous to obtain the required low partial pressure of the organic compound in the process. When steam is employed, the ratio of steam to organic compound is normally above about two mols of steam per mol or organic compound such as within the: range of about 2 or 5 to 20 or 30 mols, although larger amounts of steam as high as 40 mols have been employed. The degree of dilution of the reactants with steam and the like is related to maintaining the partial pressure of the organic compound in the system at below about.

one-third atmosphere and preferably below inches mercury absolute when the total pressure on the system is one atmosphere. For example, in a mixture of one mol of butene, three mols of steam and one mol of oxygen under a total pressure of one atmosphere the hutene would have an absolute pressure of one-fifth of the total pressure, or roughly six inches of mercury absolute pressure. Equivalent to this six inches of mercury butene absolute pressure at atmospheric pressure would be butene mixed with oxygen and bromine under a vacuum such that the partial pressure of the butene is six inches of mercury absolute. A combination of a diluent such as steam together with a vacuum may be utilized to achieve the desired partial pressure of the hydrocarbon. For the purpose of this invention, also equivalent to the six inches of mercury butene absolute pressure at atmospheric pressure would be the same mixture of one mol of butene, three mols of steam and one mol of oxygen under a total pressure greater than atmospheric, for example, a total pressure of or inches mercury above atmospheric. Thus, when the total pressure on the reaction zone is greater than one atmosphere, the absolute values for the pressure of butene will be increased in direct proportion to the increase in the total pressure above one atmosphere. Another feature of this invention is that the combined partial pressure of the hydrocarbon to be dehydrogenated plus the bromineliberating material will preferably also be equivalent to less than 10 inches of mercury, and preferably less than 6 or 4 inches of mercury, at a total pressure of one atmosphere. The lower limit of Organic compound partial pressure will be dictated by commercial considerations and normally will be greater than about 0.1 inch of mercury absolute.

The temperature of the reaction is from about 400 C. to about 800 C. or 1000 C. Preferably the temperatures will be from at least 450 C. to 900 C., and generally wil be at least about 500 C. The optimum temperature may be determined as by thermocouple at the maximum temperature of the reaction. Usually the temperature of reaction will be controlled between about 450 C. and about 750 C. or 800 C.

The flow rates of the gaseous reactants may be varied quite widely and good results have been obtained with organic compound gaseous flow rates ranging from about 0.25 to about 3 liquid volumes of organic compound per volume of reactor packing per hour, the residence or con-tact time of the reactions in the reaction zone under any given set of reaction conditions depending upon the factors involved in the reacion. Generally,- the flow rates will be within the range of about 0.10 to or higher liquid volumes of the hydrocarbon to be dehydrogenated, calculated at standard conditions of 0 C. and 760 mm. of mercury per volume of reactor space containing catalyst per hour (referring to as either LHSV or liquid v./v./hr.). Usually the LHSV will be between 0.15 and 15. The volume of reactor containing catalyst is that volume of reactor space including the volume displaced by the catalyst. For example, if a reactor has a particular volume of cubic feet of void space, when that void space is filled with catalyst particles the original void space is the volume of reactor containing catalyst for the purpose of calculating the flow rates. The residence or contact time of the reactants in the reaction zone under any given set of reaction conditions depends upon all the factors involved in the reaction. Contact times ranging from about 0.01 to about two second at about 450 C. to 750 C. have been used. A wider range of residence times may be employed, as 0.001 second to about 10 or 15 seconds. Residence time is the calculated dwell time of the reaction mixture in the reaction zone assuming the mols of product mixture are equivalent to the mols of feed mixture.

For conducting the reaction, a variety of reactor types may be employed. Fixed bed reactors may be used and fluid and moving bed systems are advantageously applied to the process of this invention. In any of the reactors suitable means for heat removal may be provided. Tubu- -lar reactors of large diameter which are loaded or packed with the solid contact mass are satisfactory.

Good results have been obtained when the exposed surface of the solid contact mass is greater than about 25 square feet, preferably greater than about 50 square feet per cubic foot of reactor as 75 or or higher. Of course, the amount of catalyst surface may be much greater when irregular surface catalysts are used. When the catalyst is in the form of particles, either supported or unsupported, the amount of catalyst surface may be expressed in terms of the surface area per unit weight of any particular volume of catalyst particles. The ratio of catalytic surface to weight will be dependent upon various factors including the particle size, particle distribution, apparent bulk density of the carrier, and so forth. T ypi cal values for the surface to weight ratio are such as about /2 to 200 square meters per gram, although higher and lower values may be used.

Excellent results have been obtained by packing the reactor with catalyst particles as the method of introducing the catalytic surface. The size of the catalyst particles may vary widely but generally the maximum particles size will at least pass through a Tyler Standard Screen which has an opening of 2 inches, and generally the largest particles of catalyst will pass through a Tyler Screen with one inch openings. Thus, the particle size when particles are used preferably will be from about 10 microns to a particle size which will pass through a Tyler Screen with openings of 2 inches. If a carrier'is used the catalyst may be deposited on the carrier by methods known in the art such as by preparing an aqueous solution or dispersion of the catalyst, mixing the carrier with the solution or dispersion until the active ingredients are coated on the carrier. The coated particles may then be dried, for example, in an oven at about C. Various other methods of catalyst preparation known to those skilled in the art may be used. Very useful carriers are the Alundums, silicon carbide, the Carborundums, pumice, kieselguhr, asbestos, and the like. When carriers are used, the amount of catalyst composition on the carirer will generally be in the range of about 2 to 80 weight percent of the total weight of the active catalytic material plus carrier. Another method for introducing the required surface is to utilize as a reactor a small diameter tube wherein the tube wall is catalytic or is coated with catalytic material. If the tube Wall is the only source of catalyst generally the tube will be of an internal diameter of no greater than one inch such as less than A inch in diameter or preferably will be no greater than about /2 inch in diameter. The technique of utilizing fluid beds lends itself well to the process of this invention.

In the above descriptions of catalyst compositions, the composition described is that of the surface which is exposed in the dehydrogenation zone to the reactants.

t That is, if a catalyst carrier is used, the composition described as the catalyst refers to the composition of the surface and not to the total composition of the surface coating plus carrier. The catalytic compositions are intimate combinations or mixtures of the ingredients. These ingredients may or may not be present as alloys. Catalyst binding agents or fillers may be used, but these will not ordinarily exceed about 50 percent or 65 percent by weight of the catalytic surface. The defined catalytic components will be the main active constituents in the catalyst and the catalyst may consist essentially of the 2 As measured by the Innes nitrogen absorption method on *a. representative unit volume of catalyst particles. The Innes is reported in Innes, W. 3., Anal. Chem., 23, 759

defined catalytic components. The weight percent of the defined catalytic atoms will generally be at least 20 percent, and are preferably at least 35 percent of the composition of the catalyst surface exposed to the reaction gases and will generally be at least 51 or about 80 atomic weight percent of any cations in the surface, such as at least 80 atomic percent of any metal cations in the surface.

The defined catalyst combinations may be employed in any form, e.g., as pellets, tablets, as coatings on carriers or supports, and the like, in both fixed and fluidized beds. Other methods of catalyst preparation known to those skilled in the art may also be used.

According to this invention, the catalyst is autoregenerative and thus the process is continuous. Little or no energy input is required for the process and it may be operated essentially adiabatically. Moreover, small amounts of tars and polymers are formed as compared to prior art processes. It is also an advantage of this invention that triple bond containing compounds are more easily obtained than with catalysts containing only one of the defined components.

In the examples given below the conversions, selectivities and yields are expressed as mol percent based on the mols of the compound to be dehydrogenated fed to the reactor. The temperature of reaction listed is approximately the maximum temperature in the reactor. The catalysts are present as fixed beds.

The Group Ia and Ila compounds used include, for example, oxides, hydroxides and salts such as the phosphates, sulfates, halides and the like. Useful compounds include, for example, lithium chloride, lithium oxide, lithium bromide, lithium fluoride, lithium phosphate, sodium hydroxide, sodium oxide, sodium chloride, sodium sulfate, beryllium oxide, sodium bromide, sodium iodide, sodium phosphate, sodium fluoride, potassium chloride, potassium bromide, potassium sulfate, potassium iodide, potassium nitrate, potassium citrate, potassium hydroxide, potassium oxide, potassium phosphate, rubidium chloride, rubidium bromide, rubidium iodide, rubidium oxide, magnesium acetate, magnesium bromide, magnesium oxide, magnesium iodide, calcium oxide, calcium acetate, calcium oxalate, calcium chloride, calcium bromide, calcium iodide, calcium phosphate, calcium fluoride, strontium oxide, strontium hydroxide, strontium chloride, strontium bromide, barium oxide, barium chloride, barium hydroxide, barium sulfate, barium bromide, barium iodide, beryllium chloride, and the like, and mixtures thereof. Preferred Group Ia and Ila metal elements are lithium, sodium, magnesium, potassium, calcium, strontium and barium, such as the oxides, phosphates, iodides, bromides, chlorides or fluorides of these metals. The oxides and halides and mixtures thereof are particularly preferred. Many of the Group Ia and Ila compounds may change during the preparation of the catalyst, during heating in a reactor prior to use in the process of this invention, or are converted to another form under the described reaction conditions, but such materials still function as an effective compound in the defined process. For example, the halides may be converted to the oxides or vice versa under the conditions of reaction. The amount of Group Ia metal compound or Group ID: metal compound with the additional metal or inorganic compound thereof may be varied quite widely and while small amounts, as low as one-tenth percent based on the total catalyst, have been used, much larger amounts may be employed in concentrations up to where the Group Ia or IIa metal compound is the larger constituent in the composition, such as up to 50 weight percent or more, as 95 percent. Normally up to 50 percent and more usually about one to about twenty-five percent of the Group la or Group IIa compound, such as about one to ten percent, with the remainder being the defined second inorganic metal compound, is satisfactory. On an atomic basis, the combined amount of the metal atoms of Group Ia and/or IIa will be from at least about 0.001 atom per atom of the defined second catalyst component and mixtures thereof. Excellent results are obtained at ratios of about 0.01 to 1.0 or 1.5 atoms of Group Ia and 11a per atom of the elements from the second specified group, such as from or about 0.01 or 0.02 to 0.5 atom of Group In and 1141 per atom of the elements from the second specified group.

A great variety of metals or metal compounds of Periodic Table Groups IVb, Vb, and VIb may be used as the second component in conjunction with the Group Ia and Ila metal compounds. Metals of the described second component group in elemental form may be employed and are included within the scope of this invention. The metals generally are changed to inorganic compounds thereof, at least on the surface, under the reaction condition-s set forth herein. Particularly effective are inorganic compounds such as the oxides and salts including the phosphates and the halides, such as the iodides, bromides, chlorides and fluorides. Inorganic compounds which are useful as the second component in the compounded contact mass for the process of this invention include titanium oxide, hafnium oxide, zirconium oxide, tungstic acid, vanadium pentoxide, tantalum oxide, chromic oxide, chromic chloride, molybdenum oxide, molybdenum phosphate, vanadium oxyphosphate, and molybdenum phosphate. Preferably the catalyst will be solid under the conditions of reaction. Excellent catalyst are those comprising atoms of titanium, zirconium, vanadium, niobium, chromium and molybdenum, such as the oxides, phosphates, iodides, bromides, chlorides or fluorides of these elements. Many of the salts, oxides and hydroxides of the metals of the listed elements may change during the preparation of the catalyst, during heating in a reactor prior to use in the process of this invention, or are converted to another form under the described reaction conditions, but such materials still function as an effective compound in the defined process. For example, many of the metal nitrates, nitrites, carbonates, hydroxides, acetates, and the like may be converted to the corresponding oxide or bromide under the reaction conditions defined herein. Salts which are stable or partially stable at the defined reaction temperatures are likewise effective under the conditions of the described reaction, as well as such compounds which are converted to another form in the reactor. At any rate, the catalysts are effective if the defined catalyst is present in a catalytic amount in contact with the reaction gases. Useful catalyst combinations include zirconium oxide and lithium chloride, zirconium oxide and lithium oxide, halfnium oxide and magnesium oxide, titanium dioxide and lithium chloride or lithium hydroxide, vanadium pentoxide and lithium oxide or rubidium oxide, tungsten oxide and potassium bromide, chromic oxide and barium hydroxide.

To show the effect of the combination catalyst containing a metal element from Group Ia and 11a together with an element of the defined second component comparative examples are made. The comparative runs were made at identical conditions.

The runs are made in a Vycor reactor which is one inch internal diameter; the overall length of the reactor is about 36 inches with the middle 24 inches of the reactor being encompassed by a heating furnace; the bottom 6 inches of the reactor is empty; at the top of this 6 inches is a retaining plate, and on top of this plate are placed 16 inches of the catalyst particles. The catalyst particles are prepared by coating the designated catalytic compounds on A; x inch Vycor Raschig rings by pouring a thin aqueous slurry of the catalytic compound through the 16 inches of rings contained in the reactor. This procedure is repeated several times until the rings are thoroughly coated with the catalyst. The coated rings are then dried in the reactor under a stream of nitrogen at a reactor temperature of approximately 500 C. On top of the dried catalyst particles are placed 6 inches of uncoated x A inch Vycor Raschig rings to form a preheat zone. The flow rates were calculated on the volume of the 16 inch long by 1 inch diameter portion of the reactor which was at or near the reaction temperature and is filled with catalyst particles. At a 700 C. maximum bed temperature, butene-2 of a purity of at least 99 mol percent is dehydrogenated to butadicne-1,3. The flow rate of butene-2 is maintained at 1 liquid volume of butene-2 (calculated at C. and 760 mm. mercury) per volume of the 16 inch section of the reactor packed with catalyst which was at or near the reaction temperature per hour (liquid v./v./hr.) The flow rate of butene-2 is 0.22 liter per minute (calculated at 0 C. and 760 mm. mercury). Oxygen and steam are also fed to the reactor at a mol ratio of oxygen to butene-2 of 0.85, and a mol ratio of steam to butene-2 of 16. Hydrogen bromide is added as an aqueous solution at a rate which is equivalent to 0.028 mol of bromine (cal culated as Br per mol of butene-2. The steam, butene- 2, oxygen and aqueous solution of hydrogen bromide are added at the top of the reactor. The conversion of butene-2 is reported as mol percent. The percent selectivity to butadiene-1,3 and the resulting yield of butadiene-1,3 are reported as mol percent butadiene-1,3 based on the amount of butene-2 fed to the reactor.

Example 1 The catalyst is TiO The conversion is 91 percent, the selectivity is 74 percent, and the yield is 67 percent.

Example 2 Example 1 is repeated with the exception that the catalytic coating on the Vycor rings consists of by weight 98 percent Ti0 and 2 percent KCl. The conversion is 81 percent, the selectivity is 89 percent and the yield is 72 percent.

Example 3 The catalyst is Nb O The conversion is 85 percent, the selectivity is 65 percent and the yield is 55 percent.

Example 4 Example 3 is repeated with the excepton that the catalytic coating on the Vycor rings consists of by weight 95 percent Nb O and 5 percent LiCl. The conversion is 84 percent, the selectivity is 75 percent and the yield is 63 percent.

Example 5 The catalyst is M00 The conversion is 89 percent, the selectivity is 63 percent and the yield is 56 percent.

Example 6 Example 5 is repeated with the exception that the catalytic coating on the Vycor rings consists of by weight 95 percent M00 and 5 percent BaO. The conversion is 88 percent, the selectivity is 81 percent and the yield is 71 percent.

Example 7 Isopentane is dehydrogenated to a mixture of isoprene and amylenes. The catalyst consists of by weight a mixture of 80 percent TiCl and 20 percent KCl. The flow rate is 0.5 LHSV and bromine, steam and oxygen are employed in ratios of 0.11, 15 and 1.5 mols respectively per mol of isopentane. At a reactor temperature of 475 C. the selectivity is 86 mol percent.

Example 8 n-Butene is dehydrogenated to butadiene-1,3 using as a catalyst a mixture of 91 percent by weight TiO and 9 percent by weight CaO. Steam, oxygen and bromine (as HBr) are employed in amounts of 12.5, 0.7 and 0.01 mols respectively per mol of butene. The selectivity at 623 C. is 81 mol percent.

10 Example 9 The catalyst is by weight 91 percent CrCl and 9 percent CaCl Butene-2 is dehydrogenated using 12.5 mols of steam, 0.7 mol of oxygen and 0.01 mol of bromine (fed as HBr) per mol of butene. The LHSV for an 8 inch catalyst bed is 1.0. At a reactor temperature of 575- 635 C. the selectivity to butadiene-l,3 is 60 percent.

Example 10 Isopentane is dehydrogenated to a mixture of isoprene and amylenes. The catalyst is percent CrCl and 20 percent KCl. The flow rate is 0.5 LHSV and the steam and oxygen ratios are 15 and 1.5 mols respectively per mol of isopentane. Using 0.22 mol of bromine (fed as HBr) per mol of isopentane and a reactor temperature of 475 C. the selectivity is 68 percent.

Example 11 Butene together with 12.5 mols of steam, 0.7 mol of oxygen and .01 mol of bromine (fed as HBr) per mol of butene is passed over a catalyst bed of 72.0 percent M00 and 28.0 percent CaO. The flow rate is 1.0 LHSV. At a temperature of 688 C. the selectivity is 91 percent.

The process of this invention is particularly applicable to the dehydrogenation of hydrocarbons, including dehydroisomerization and dehydrocyclization, to form a variety of acyclic compounds, cycloaliphatic compounds, aromatic compounds and mixtures thereof. For example, 2- ethylhexene-l may be converted to a mixture of aromatic compounds such as toluene, ethyl benzene, p-xylene, oxylene and styrene.

I claim:

1. The method for dehydrogenating hydrocarbon compounds having 2 to 20 carbon atoms to produce a dehydrogenated product having the same number of carbon atoms and the same structure with the exception of the removed hydrogen atoms which comprises heating in the vapor phase at a temperature of above 400 C. a hydrocarbon compound having a group with oxygen in a molar ratio of greater than onefourth mol of oxygen per mol of said hydrocarbon compound, bromine in an amount of less than 0.5 mol of bromine per mol of said hydrocarbon compound, the ratio of the mols of said oxygen to the mols of said bromine being at least 2.5, the partial pressure of said hydrocarbon compound being equivalent to less than one-half the total pressure in the presence of a catalyst comprising as its main active constituent (1) a compound selected from the group consisting of oxides, salts and hydroxides of alkali and alkaline earth metals and mixtures thereof, and (2) a metal or metal compound of Periodic Table Groups IVb, Vb and VII; and mixtures thereof.

2. The method of claim 1 wherein the said compound is a hydrocarbon having from 2 to 12 carbon atoms.

3. The method of claim 1 wherein the said compound is an acyclic aliphatic hydrocarbon of 4 to 6 carbon atoms.

4. The method of claim 1 wherein the said compound is a hydrocarbon selected from the group consisting of nbutene, n-butane, isopentene, isopentane and mixtures thereof.

5. The method of claim 4 wherein the said temperature is at least 450 C.

6. The method of claim 4 wherein steam is employed in the said vapor phase in an amount of from 2 to 30 mols of steam per mol of said hydrocarbon.

7. The method of claim 4 wherein the oxygen is present in an amount of greater than 3.0 mols of oxygen per mol of said bromine and the said bromine is present in an amount of from .001 to .09 mol of bromine per mol of said hydrocarbon.

8. The method of claim 4 wherein the alkali and alkaline earth metal compounds are preesnt in an amount of from about .01 to 0.5 atom of the alkali or alkaline earth metal elements per atom of the metal elements of the said (2).

9. The method of claim 4 wherein the bromine is present in an amount of no greater than 10 mol percent of the total gaseous mixture in the dehydrogenation zone.

10. A method for dehydrogenating hydrocarbons containing 4 to 5 carbon atoms which comprises reacting in the vapor phase at a temperature between 400 C. and about 750 C. an aliphatic hydrocarbon containing 4 to 5 carbon atoms with oxygen in a molar ratio of about 0.4 mol to about 2 mols of oxygen per mol of hydrocarbon, and above 0.001 mol to less than 0.2 mol per mol of aliphatic hydrocarbon of bromine, at a partial pressure of said hydrocarbon of less than about one-third the total pressure in the presence of a mixture of (1) a compound selected from the group consisting of alkali metal oxides, alkaline metal hydroxides, alkaline earth metal oxides and alkaline earth metal hydroxides, and (2) an inorganic metal compound selected from the group consisting of Periodic Table Groups IVb, Vb, V111 and mixtures thereof.

11. The method of claim 1 wherein the said (1) is selected from the group consisting of lithium, sodium, magnesium, potassium, calcium, strontium, barium and mixtures thereof.

12. The method of claim 11 wherein the said (2) is titanium.

13. The method of claim 11 wherein the said (2) is molybdenum.

14. The method of claim 11 wherein the said (2) is chromium.

15. The method of claim 11 wherein the said (2) is niobium.

16. The method of claim 1 wherein the said (1) and (2) are present as oxides, halides or mixtures thereof.

References Cited by the Examiner UNITED STATES PATENTS 9/1955 Kalb 260669 9/1965 Bajars 260680 

1. THE METHOD FOR DEHYDROGENATING HYDROCARBON COMPOUNDS HAVING 2 TO 20 CARBON ATOMS TO PRODUCE A DEHYDROGENATED PRODUCT HAVING THE SAME NUMBER OF CARBON ATOMS AND THE SAME STRUCTURE WITH THE EXCEPTION OF THE VAPOR PHASE AT A TEMPERATURE OF ABOVE 400*C. A HYDROCARBON COMPOUNDS HAVING A >CH-CH< GROUP WITH OXYGEN IN A MOLAR RATIO OF GREATER THAN ONEFOURTH MOL OF OXYGEN PER MOL OF SAID HYDROCARBON COMPOUND, BROMINE IN AN AMOUNT OF LESS THAN 0.5 MOL OF BROMINE PER MOL OF SAID OXYGEN TO THE MOLS OF SAID BROMINE BEING AT LEAST 2.5, THE PARTIAL PRESSURE OF SAID HYDROCARBON COMPOUND BEING EQUIVALENT TO LESS THAN ONE-HALF THE TOTAL PRESSURE IN THE PRESENCE OF A CATALYST COMPRISING AS ITS MAIN ACTIVE CONSTITUENT (1) A COMPOUND SELECTED FROM THE GROUP CONSISTING OF OXIDES, SALTS AND HYDROXIDES OF ALKALI AND ALKALINE EARTH METALS AND MIXTURES THEREOF, AND (2) A METAL OR METAL COMPOUND OF PERIODIC TABLE GROUPS IVB, VB AND VIB AND MIXTURES THEREOF. 